Papers by Keyword: Energy Criterion

Abstract: The paper presents the research on the controlled strain and temperature on the stress strength of martensitic GX12CrMoVNbN9 – 1 in the energy-based approach. The fatigue tests were carried out for five levels of total strain amplitude ac and two temperatures (the room one and 600oC). Performed research has shown that in terms of energy the investigated cast steel is characterized by changes in cyclic properties. Moreover, it has been proved that the temperature of study significantly influences the per-unit value of strain energy. The influence is slight in the area of large strains and gets stronger as the level of cyclic strains decreases.

Abstract: Under the action of stress and crack hydraulic pressure, the damage and rupture of jointed rock mass accumulate and extend simultaneously during the process of its crack occurrence and growth. The rock mass’s damage will be accumulated owing to its rupture, and the damage is closely related to the rupture. Taking into account comprehensive the stress intensity factors both of plane stress and plane strain for hydrous jointed rock mass, two new equations of crack propagation and the new crack length were built on the basis of energy criterion. Assuming the jointed rock mass as equivalent continuous mass with damage and introducing the damage constitutive equation of rock, the damage evolution of the hydrous jointed rock mass is simulated by the damage tensor and the damage strain. The model is used to simulate one tunnel. Through simulation, the waterhead contour is more smooth when the coupling is considered than is not considered, and the maximal displacement almost the same because the diversion tunnel was bulit.The simulate results can provide a reasonable recommendation to the engineering practices.

Abstract: The evaluation on energy characteristics of earthquake-excited building structures with seismic protection devices is actively carried out in this study. The mechanical model of passive friction dampers is first introduced and the dynamic model of building-damper system is proposed. The evaluation criteria of energy responses are developed and applied to the earthquake response mitigation of a real multi-story building incorporated with friction dampers. The observations indicate that the earthquake-induced vibration of the structure can be substantially suppressed and the proposed energy evaluation criteria can be effectively utilized in the examination on seismic mitigation performance.

Abstract: An energy-based criterion is introduced in order to investigate the nonlinear dynamic response of RC beams subject to rapid and unexpected damages. Since only static pushover analysis is necessary, the structural behavior of the damaged members can be evaluated with a new simplified procedure. It is firstly applied to the case of elastic–perfectly plastic continuous beam, when one of the supports is quickly removed. In such a situation, the proposed procedure gives satisfactory results if compared to those of a more rigorous dynamic analysis. By means of a nonlinear static analysis, which encompasses also the post-peak response, the energy-based approach is also applied to concrete beams. More specifically, it is used to predict the bearing capacities of reinforced concrete beams, having different steel rebars, when they suddenly lose a single support.

Abstract: This paper is addressed to the optimal control of the simply supported sandwich panel with pyramidal truss cores. Firstly, according to the sandwich theory proposed by Sorokin and Ershova, the eigenfrequencies of the sandwich panel are studied. Then based on the energy criterion, the weight coefficient matrix Q and R for the linear quadratic regulator method are obtained. By solving the Riccati equation, the displacement and control force are given. The curves for the displacement response at the center of the plate are shown. From the numerical results, it is found that this method is effective in suppressing the vibration of the sandwich panel with pyramidal truss cores.

Abstract: This paper presents the adaptation of the analytical method for transverse laminacracking in multidirectionally laminated composites to the finite element method. The damageinitiation and extension in a structure made of the laminated composite are evaluated by thedeveloped finite element method. The reduction in the stiffness of the laminated composite thatcaused by the crack growth is evaluated by the total force method. In the present analyses by thedeveloped method, the critical strain of the crack growth is the value of the strain which satisfiesboth energy criterion and stress criterion. To demonstrate the accuracy of the developed method,the analytical results of crack growth in CFRP quasi-isotropic laminate with a circular hole arecompared with experimental results.